Natural humic acid, which is formed from the plant and animal remains after long-term and complicated biochemical reaction, mainly exists in soil and lean coal such as peat coal, weathered coal and brown coal. Natural humic acid belongs to un-renewable natural resources, and its alkaline extract, called coal humic acid or mineral humic acid, is the current major humic acid product which has realized industrialization and has been used in industry and agriculture. However, biochemical humic acid (BHA) is a product rich in humic acid, which is produced from the organic waste as raw material by special biochemical process. The available organic wastes from industry, agriculture and daily life are mainly crop straw, food processing waste, excrement of livestock and poultry, residue of sugar industry, black liquid from paper industry, waste liquid of alcohol and gourmet powder, garden waste etc. Thus, BHA is an “artificial humic acid” and a new source of humic acid. Since the raw material of BHA is the waste instead of natural resource, developing BHA can effectively solve the problem of depending on un-renewable natural resources. Research (He Liqian, 1999) shows that, BHA not only has general characteristics and properties of the humic acid, but also has characteristics different from ordinary humic acid: 1) having low extent of condensation, low carbon content, and small molecular weight, being easy to be absorbed and utilized by organisms; 2) containing more functional groups, having stronger physiological activity than ordinary humic acid; 3) having light color, and better water solubility, being soluble in acidic or alkaline solution; 4) having high flocculation limit and big buffer capacity.
In agricultural production, the humic acid fertilizer possesses the following significant efficacy: increasing production and improving quality. The humic acid and trace elements in humic acid fertilizer form a complex compound or chelate compound which is easily dissolved and easy to be absorbed by crops, which is helpful for root system and leaf surface to absorb trace elements. The functional groups of humic acid such as carboxyl, phenolic hydroxyl group, which have strong ion exchange and adsorption ability, can reduce the loss of ammonium nitrogen to increase the utilization rate of nitrogen fertilizer; inhibit soil to fix the water-soluble phosphorus, change quick-acting phosphorus into slow-acting phosphorus and enhance the root system to absorb phosphorus; absorb and store potassium ion so as to make the potassium fertilizer degrade slowly, increase the release amount of the potassium, and thus increase the amount of quick-acting potassium. A variety of active functional groups in the humic acid molecular can enhance physiological metabolism, as well as growth and development of plants. Thus, the humic acid fertilizer can effectively increase utilization rate of the nutrients and stimulate the growth of crops, thus increasing yield and quality of crops.
The humic acid fertilizer also possesses the following significant efficacy: improving the resistance of crops. The humic acid fertilizer can decrease opening extent of plant leaf stomata and reduce leaf transpiration, thus decreasing water consumption of plant, improving the internal water condition in plant and enhancing its anti-drought ability. The humic acid fertilizer also can inhibit fungi, strengthen disease resistance of crops, avoid rot disease, root rot disease etc., and alleviate the damage from diseases and insect pest.
The humic acid fertilizer also possess the following significant efficacy: improving soil and reducing pollution. The humic acid fertilizer can enhance the formation of soil granular structure, reduce soil bulk density, increase the substitution amount of positive ion, and adjust soil acidity and alkalinity, so as to increase the soil's ability of water retention, fertilizer retention, heat preservation and ventilation.
The physicochemical properties of humic acid endows it the following advantages to serve as a fertilizer:                1. Improvement of Low Yield Soil: two thirds of the area of cultivated land in China is low-middle yield soil. Research (Xing Shuji, 1989) indicates that, applying large quantity of humic acid fertilizer throughout China can lead to a certain improvement in the arable soil or rhizosphere soil. There is a large area of red soil distributed in south China, the characteristics of such red soil are “acidic, barren, hard and dried”, as well as lacking organic matter and nutrients, and having bad soil structure. The saline-alkali soils in China are mainly distributed in northwest China, north China, northeast China and the coastal areas, including saline soil and alkali soil. The major harms of the saline-alkali soils are: high soil salt content, too high concentration of the harmful ions; too high soil alkality; bad soil structure; inhibition of the growth and development of crops. Applying large quantity of the humic acid fertilizer for a long time can enhance the formation of soil aggregate and adjust the soil condition of “water, fertilizer, air and heat”; and can also inhibit the increase of salinity, reduce salt content of the topsoil, and change the pH values of saline-alkali soils through “salt-separating” and “salt-absorbing” effects, thus greatly increasing the survival rate of crops.        2. Increase of Effect and Slow Release of Chemical Fertilizer: at present in China, the utilization rate of nitrogen fertilizer, phosphorus fertilizer and potassium fertilizer accounts for about 20% to 30%, 10% to 20% and 50% to 70% respectively. How to improve the utilization rate of chemical fertilizer has become a very important research topic in the world. The humic acid fertilizer, which is produced through adding nitrogen, phosphorus, potassium and trace elements to the raw materials of peat coal, brown coal and weathered coal, can improve the utilization rate of chemical fertilizer in different degrees; this result has been verified by a large number of research reports from China and abroad (Li Li et al., 1998). For example, the typical nitrogen fertilizer such as urea and ammonium bicarbonate generally have high volatility and low utilization rate. However, their absorption can be improved and the utilization rate can be increased by 20% to 40% after mixing the nitrogen fertilizers with humic acid to form a humic acid fertilizer. Addition of nitro humic acid to urea can form a complex of humic acid and urea, make the decomposition of urea slow, prolong the fertilizer efficiency, and reduce the loss, so that the production-increasing effect of urea can be relatively increased by 30%, and the fertilizer efficiency can be increased by over 15%. The determination results of the utilization rate of nitrogen fertilizer indicates that, after adding humic acid, the utilization rate is increased from 30.1% to 34.1%, and the nitrogen uptake is increased by 10%.        3. Modulation of Growth and Development of Crops: the efficient biological active substances contained in the humic acid fertilizer can enhance physiological metabolism, growth and development of crops, and this characteristics is not possessed by ordinary fertilizer. The ways including seed soaking, root soaking, spraying, irrigating and being as base-fertilizer with a certain concentration of humic acid fertilizer have significant effects of stimulation on various crops. Applying humic acid fertilizer improves seed germination, and the germination rate is increased by 10% to 30%; root dipping or root soaking with humic acid fertilizer has become an agriculture technical measure to improve survival rate in sticking or transplanting. Applying humic acid fertilizer makes the crops grow very well, and improves the yield and quality of the crops. Applying humic acid fertilizer can also effectively increase the anti-drought and anti-frigidity abilities of crops, and prevent underground plant diseases, insect pests and pathogenic bacteria.        
Kitchen waste refers to leftover bits and pieces and leftovers derived from hotels, restaurants, dining-halls etc., and it comprises processed food products and their residues, such as foodstuff (rice and flour), fruits and vegetables, plant and animal fats, meats, aquatic product, eggs, meat bones, and fish bone, etc. (Li Jun et al., 2009). The major chemical ingredients of kitchen waste are starch, protein, fat, cellulose, inorganic salt, which has high content of moisture, generally reaching up to 60% to 80%. There are mainly three types of kitchen waste in China: 1. domestic kitchen waste, which is classified into household kitchen waste by the China Ministry of Housing and Urban-Rural Development in 2009; 2. kitchen waste from dining-halls, restaurants, hotels, and staff dining-halls of government agencies, enterprises and public institutions, which is also an important source of kitchen waste; 3. kitchen waste from dining-halls of colleges and universities. According to a statistics from the Department of Environmental Science and Engineering in Tsinghua University, over 60 million tons of kitchen waste is generated in urban areas of China every year. The kitchen waste reaches up to 1200 tons in Beijing every day (Zhang Qing et al., 2010). The kitchen waste in China has a big total amount, and contains much fat, moisture, salt and other complex ingredients; if not treated properly, it is likely to cause food security problems such as “illegal cooking oil”, “swill-feeding swine”, thus resulting in wasting resources and influencing the ecological environment.
Generally speaking, the technology and policy on kitchen waste treatment in China are experiencing an exploring stage, and the management system and corresponding policy on kitchen waste treatment are being improved. At present the general ways of treating kitchen waste includes landfilling, burning, feed-processing technology and aerobic fermentation composting. Landfilling may cause the waste of land, while it will produce a great quantity of malodorous gas and permeated liquid, thus leading to secondary pollution to environment; burning treatment consumes much energy and produces cancer-causing substance dioxin; feed-processing technology is one of the major ways of kitchen waste treatment. In addition, illegally transporting the kitchen waste to farm for feeding swine or refining the “illegal cooking oil” causes secondary pollution to environment and potential safety harzard. The quality of fertilizers produced by anaerobic fermentation composting is poor; meanwhile, high-quality composting ways cost too much, and thus are difficult to disseminate. Since the current ways of treating kitchen waste lead to some problems in different extent, it is desired to develop a new process and new technology to increase the level of resource processing of kitchen waste.
Since 1980s, the experiment and research work regarding large-scale harmless utilization of kitchen waste has begun in some countries including Germany, France, UK, Cuba, Netherlands, US, Japan and South Korea. Achievements in the methods of collecting and treating kitchen waste and the products of kitchen waste processing have been obtained; also large-scale factories of treating kitchen waste are built in medium and large-sized cities; the treatment of kitchen waste has realized the specialization and its management has been legalized (Li Jun, 2009). At present, the major ways of treating kitchen waste out of China are also focusing on composting, landfilling, feed-processing technology and power generation and heat supply with biogenic gas. In US, the treatment ways mainly include recycling, composting and being feed; in US, the treatment way of composting is used in the Middle-West area, mainly in prisons and schools where the kitchen waste is centrally collected. Currently, vermicomposting and in-vessel composting are generally applied. The traditional treatment way in Japan is composting, which can transforms the food waste into organic fertilizers and soil conditioners. In recent years, feed-processing technology is the major way of treating kitchen waste in some of East Asian countries such as South Korea and Japan which have large population with relatively little land.
At present, the method of preparing BHA in China and abroad is performed by inoculating a plurality of special microbial bacteria strains in plant medium, namely, agricultural organic waste such as crop straw, saw dust and bagasse, fermenting by chemical or microbial fermentation technology and isolating to obtain BHA (Liu Kexing et al., 2008; Ye Shuiying, 1999). There is no report in China and abroad on producing biochemical humic acid from kitchen waste as culture medium.